Monitoring Population Dynamics of Leafhoppers and Planthoppers in Paddy Fields in the Subtropical Region of Bhutan Using Light Trap

Tshelthrim Zangpo, Ratu Kinley, Chinta Mani Dhimal, Tashi Dawa, Sonam Gyeltshen, Thirtha Maya Ghalley, Tshencho Dem, Ugyen Tshering, Jigme Wangchuk & Yeshey Dema

Rice is an important cereal crop for food security in Bhutan, but its production is threatened by many insect pests including planthoppers and leafhoppers. This study monitored and analyzed the population dynamics of green leafhopper, brown planthopper, white-backed planthopper, and zigzag leafhopper using commercial light traps in two Gewogs of Sarpang Dzongkhag: Chuzergang Gewog (Dawathang in 2018, 2020, and 2021; Karbithang in 2018) and in Samtenling Gewog (ARDC Samtenling in 2020, 2021, and 2022; farmer’s field in Samtenling in 2022. The results showed variation in hopper populations between monitoring sites and time period. Green leafhopper was consistently the most abundant species across all sites and years, with mean trap counts ranging from 182 to 1,736 individuals per trap. In contrast, brown planthopper showed fluctuating trends, peaking at 608 per trap in some sites and declining to below 100 in others. White backed planthopper and zigzag leafhopper remained relatively low, with trap means ranging from near zero to 331 and 258, respectively. Relative abundance data showed these similar patterns, with green leaf hopper dominating the hopper composition, comprising 52.7%–69.1% of populations across sites. In contrast, white backed planthopper and zigzag leafhopper represented the least abundant species. Across rice growth stages at four monitoring sites, mean hopper counts were lowest during tillering, increased significantly during booting, and peaked at grain-filling. The highest pest pressure occurred during grain-filling, with green leafhopper and brown planthopper being the most abundant. Populations declined at maturity. These findings underscore the importance of monitoring hopper populations across different sites and time periods to better understand their dynamics. Additionally, it is important to implement targeted pest management strategies during critical growth stages, particularly booting and grain-filling, to effectively mitigate hopper pressure and reduce crop losses.

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